This invention was developed to improve upon the single pivot decoupler pylon. The decoupler pylon is designed to suppress flutter and vibration of aerodynamic structures carrying pylon-mounted stores. Such stores are most commonly found under aircraft wings or fuselages in the form of weapons or fuel tanks.
The flutter desired to be suppressed is a dangerous aerodynamic instability affecting lifting surfaces moving through fluids at sufficiently high velocities. The velocity at which flutter develops in a given structure is that structure's characteristic flutter speed. Flutter speed can be a critical limitation on an aircraft's operating envelope: flying in excess of the flutter "speed limit" can result in catastrophic disintegration of the aircraft. The attachment of stores to an aircraft typically restricts its operating envelope by reducing the flutter speed. This effect is caused by the coupling of store oscillations with support surface oscillations, thus resulting in compound oscillations of dangerous magnitude developing at lower velocities. The decoupler pylon, then, suppresses flutter by decoupling the store oscillations from the support surface oscillations.
Another problem presented by flutter other than its potential for destruction of aircraft is its unpredictability; although store-induced flutter speed reductions are easily observed, such reductions are difficult to quantitatively predict. In the case of military aircraft, the difficulty of prediction is largely due to the multiple store configurations dictated by modern combat and surveillance capability requirements: a single aircraft commonly must have the flexibility to accommodate different numbers of different store types at different locations on the aircraft. These differences in store number, type, and mounting location give rise to complex multi-variable oscilation coupling patterns, and can give an aircraft as many different flutter speeds as store configurations. The theory of such store coupling is not well developed, and thus determining all of the possible flutter speeds usually requires extensive testing. The decoupler pylon, then, by suppressing flutter, obviates the need for extensive testing to determine flutter speed reductions.
Reed's single pivot pylon, shown in U.S. Pat. No. 4,343,447, comprised both passive and active suppression elements; Reed's pylon used dashpot-type passive elements and a low frequency servo control active element. A damper was also employed to damp transient oscillations of an attached store. This pylon effectively suppressed flutter of the store/support surface combination, but the single pivot design had some drawbacks. Among these drawbacks were the following: a (relatively) high number of store excursions, a high maximum pitch deflection angle, a high frequency of alignment control system activation, high force and power requirements for the alignment system, and a relatively large space requirement for the alignment system.
Accordingly, it is an object of the present invention to provide a flutter-suppressing decoupler pylon permitting fewer store excursions than permitted by a single pivot decoupler pylon.
Another object of this invention is to provide a decoupler pylon permitting a smaller maximum pitch deflection angle than permitted by a single pivot decoupler pylon.
Another object of the invention is to provide a decoupler pylon requiring less frequent activation of its alignment control system than required by a single pivot decoupler pylon.
Another object of this invention is to provide a decoupler pylon having smaller force and power requirements for its alignment control system than those of a single pivot decoupler pylon.
Another object of this invention is to provide a decoupler pylon requiring less mounting space on a support surface than required by a single pivot decoupler pylon.
Yet another object of this invention is to provide a decoupler pylon with a remote pivot.